13 years ago
Did anyone else notice John Iovine's article "How to Make
Bi-Directional Flex Sensors" in the June issue of Nuts & Volts
While resistive flex sensors have been available for several years,
they haven't been cheap, and the shape options have been a bit
limited. Mr. Iovine's article suggests that these could be
home-built, shaped-to-order, and inexpensive enough that that many
of these could be added to a robot without blowing a hobbyist's
The sensor design seemed simple enough: a sandwich made up of a
strip of thin and flexible plastic (stiffener), two strips of thin
copper surrounding a resistive layer of some sort, and shrink-wrap
tubing to keep the ham and cheese... er, "conductive layers" from
squishing out. The resistive layer might be tricky (_cloth_??), but
I was fairly sure I had some black conductive bags around here
"somewhere" (translation: only a day or two of digging ).
And it looks like Mr. Iovine's approach would make it possible to
design (say) a flex sensor that could report, with reasonable
accuracy, human finger flexing by using a "club sandwich"
Layer Cu3 might look like this from above (not to scale) if you
wanted all terminals to be at one end of the sensor:
So I went exploring Saturday afternoon. It looks like I need a new
set of places to look for oddments: the two big local art/craft
stores (Micheals, Ben Franklin) could provide sheet copper for
"embossing", but two thicknesses of their 36ga stuff seemed a bit
stiff for small robot sensors. No luck on flexible plastic.
Home Depot had some rolls of copper sheet ("roof flashing") that
seemed a bit thinner, but I didn't need 12"x20' of it, not at
$33/roll. No plastic there, either. Fortunately we have one "real"
hardware store here in Richmond -- Pleasants -- but I foolishly
didn't start with them, and now I'm temporarily sidetracked.
The article mentions that parts and pre-built sensors can be ordered
from the Images Scientific Instruments 'web site:
Images Scientific Instruments
(Based on the prices quoted there, it looks like $12 would purchase
enough material for 12 0.3"x5" sensor strips.)
Has anyone else tried making one of these? If so, what did you use,
and what were your results?
The vice of the modern notion of mental progress is that it is
always concerned with the breaking of bonds, the effacing of
boundaries, the casting away of dogmas. But if there is such a
thing as mental growth, it must mean the growth into more and
more definite dogmas. The human brain is a machine for coming to
conclusions; if it cannot come to conclusions it is rusty.
-- G.K. Chesterton: Concluding Remarks on the
Importance of Orthodoxy (1905)
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut mined spring dawt cahm (y'all)